/*
 * Modified from Polarssl here
 * http://polarssl.org/show_source?file=md5
 * under GPL2 or later
 */

#include <string.h>
#include <stdio.h>

#ifdef __cplusplus
extern "C" {
	#include <cstddef>
#endif
		#define GET_ULONG_LE(n, b, i)                        \
		{                                                    \
			(n) = ((unsigned long)(b)[i])		     \
			| ((unsigned long)(b)[(i) + 1] <<  8)        \
			| ((unsigned long)(b)[(i) + 2] << 16)        \
			| ((unsigned long)(b)[(i) + 3] << 24);       \
		}

		#define PUT_ULONG_LE(n, b, i)			     \
		{						     \
			(b)[i] = (unsigned char)(n);		     \
			(b)[(i) + 1] = (unsigned char)((n) >>  8);   \
			(b)[(i) + 2] = (unsigned char)((n) >> 16);   \
			(b)[(i) + 3] = (unsigned char)((n) >> 24);   \
		}

		static const unsigned char md5_padding[64] = {
			0x80, 0, 0, 0, 0, 0, 0, 0,
			0, 0, 0, 0, 0, 0, 0, 0,
			0, 0, 0, 0, 0, 0, 0, 0,
			0, 0, 0, 0, 0, 0, 0, 0,
			0, 0, 0, 0, 0, 0, 0, 0,
			0, 0, 0, 0, 0, 0, 0, 0,
			0, 0, 0, 0, 0, 0, 0, 0,
			0, 0, 0, 0, 0, 0, 0, 0,
		};

		static const unsigned long state_init[] = {
			0, 0, 0x67452301, 0xEFCDAB89, 0x98BADCFE, 0x10325476
		};

		static void
		md5_process(unsigned long *state, const unsigned char *data)
		{
			unsigned long X[16], A, B, C, D;
			int v;

			for (v = 0; v < 16; v++)
				GET_ULONG_LE(X[v], data, v << 2);

		#define S(x, n) ((x << n) | ((x & 0xFFFFFFFF) >> (32 - n)))

		#define P(a, b, c, d, k, s, t) { a += F(b, c, d) + X[k] + t; a = S(a, s) + b; }

			A = state[0];
			B = state[1];
			C = state[2];
			D = state[3];

		#define F(x, y, z) (z ^ (x & (y ^ z)))

			P(A, B, C, D,  0,  7, 0xD76AA478);
			P(D, A, B, C,  1, 12, 0xE8C7B756);
			P(C, D, A, B,  2, 17, 0x242070DB);
			P(B, C, D, A,  3, 22, 0xC1BDCEEE);
			P(A, B, C, D,  4,  7, 0xF57C0FAF);
			P(D, A, B, C,  5, 12, 0x4787C62A);
			P(C, D, A, B,  6, 17, 0xA8304613);
			P(B, C, D, A,  7, 22, 0xFD469501);
			P(A, B, C, D,  8,  7, 0x698098D8);
			P(D, A, B, C,  9, 12, 0x8B44F7AF);
			P(C, D, A, B, 10, 17, 0xFFFF5BB1);
			P(B, C, D, A, 11, 22, 0x895CD7BE);
			P(A, B, C, D, 12,  7, 0x6B901122);
			P(D, A, B, C, 13, 12, 0xFD987193);
			P(C, D, A, B, 14, 17, 0xA679438E);
			P(B, C, D, A, 15, 22, 0x49B40821);

		#undef F

		#define F(x, y, z) (y ^ (z & (x ^ y)))

			P(A, B, C, D,  1,  5, 0xF61E2562);
			P(D, A, B, C,  6,  9, 0xC040B340);
			P(C, D, A, B, 11, 14, 0x265E5A51);
			P(B, C, D, A,  0, 20, 0xE9B6C7AA);
			P(A, B, C, D,  5,  5, 0xD62F105D);
			P(D, A, B, C, 10,  9, 0x02441453);
			P(C, D, A, B, 15, 14, 0xD8A1E681);
			P(B, C, D, A,  4, 20, 0xE7D3FBC8);
			P(A, B, C, D,  9,  5, 0x21E1CDE6);
			P(D, A, B, C, 14,  9, 0xC33707D6);
			P(C, D, A, B,  3, 14, 0xF4D50D87);
			P(B, C, D, A,  8, 20, 0x455A14ED);
			P(A, B, C, D, 13,  5, 0xA9E3E905);
			P(D, A, B, C,  2,  9, 0xFCEFA3F8);
			P(C, D, A, B,  7, 14, 0x676F02D9);
			P(B, C, D, A, 12, 20, 0x8D2A4C8A);

		#undef F

		#define F(x, y, z) (x ^ y ^ z)

			P(A, B, C, D,  5,  4, 0xFFFA3942);
			P(D, A, B, C,  8, 11, 0x8771F681);
			P(C, D, A, B, 11, 16, 0x6D9D6122);
			P(B, C, D, A, 14, 23, 0xFDE5380C);
			P(A, B, C, D,  1,  4, 0xA4BEEA44);
			P(D, A, B, C,  4, 11, 0x4BDECFA9);
			P(C, D, A, B,  7, 16, 0xF6BB4B60);
			P(B, C, D, A, 10, 23, 0xBEBFBC70);
			P(A, B, C, D, 13,  4, 0x289B7EC6);
			P(D, A, B, C,  0, 11, 0xEAA127FA);
			P(C, D, A, B,  3, 16, 0xD4EF3085);
			P(B, C, D, A,  6, 23, 0x04881D05);
			P(A, B, C, D,  9,  4, 0xD9D4D039);
			P(D, A, B, C, 12, 11, 0xE6DB99E5);
			P(C, D, A, B, 15, 16, 0x1FA27CF8);
			P(B, C, D, A,  2, 23, 0xC4AC5665);

		#undef F

		#define F(x, y, z) (y ^ (x | ~z))

			P(A, B, C, D,  0,  6, 0xF4292244);
			P(D, A, B, C,  7, 10, 0x432AFF97);
			P(C, D, A, B, 14, 15, 0xAB9423A7);
			P(B, C, D, A,  5, 21, 0xFC93A039);
			P(A, B, C, D, 12,  6, 0x655B59C3);
			P(D, A, B, C,  3, 10, 0x8F0CCC92);
			P(C, D, A, B, 10, 15, 0xFFEFF47D);
			P(B, C, D, A,  1, 21, 0x85845DD1);
			P(A, B, C, D,  8,  6, 0x6FA87E4F);
			P(D, A, B, C, 15, 10, 0xFE2CE6E0);
			P(C, D, A, B,  6, 15, 0xA3014314);
			P(B, C, D, A, 13, 21, 0x4E0811A1);
			P(A, B, C, D,  4,  6, 0xF7537E82);
			P(D, A, B, C, 11, 10, 0xBD3AF235);
			P(C, D, A, B,  2, 15, 0x2AD7D2BB);
			P(B, C, D, A,  9, 21, 0xEB86D391);

		#undef F

			state[0] += A;
			state[1] += B;
			state[2] += C;
			state[3] += D;
		}

		static
		void md5_update(unsigned long *state, unsigned char *buffer,
							   const unsigned char *input, int ilen)
		{
			int fill;
			unsigned long left;

			if (ilen <= 0)
				return;

			left = state[0] & 0x3F;
			fill = 64 - left;

			state[0] += ilen;
			state[0] &= 0xFFFFFFFF;

			if (state[0] < (unsigned long)ilen)
				state[1]++;

			if (left && ilen >= fill) {
				memcpy(buffer + left, input, fill);
				md5_process(&state[2], buffer);
				input += fill;
				ilen -= fill;
				left = 0;
			}

			while (ilen >= 64) {
				md5_process(&state[2], input);
				input += 64;
				ilen -= 64;
			}

			if (ilen > 0)
				memcpy(buffer + left, input, ilen);
		}

		void
		MD5(const unsigned char *input, int ilen, unsigned char *output)
		{
			unsigned long last, padn;
			unsigned long high, low;
			unsigned char msglen[8];
			unsigned long state[6];
			unsigned char buffer[64];

			memcpy(&state[0], &state_init[0], sizeof(state_init));

			md5_update(state, buffer, input, ilen);

			high = (state[0] >> 29) | (state[1] <<  3);
			low  = state[0] <<  3;

			PUT_ULONG_LE(low, msglen, 0);
			PUT_ULONG_LE(high, msglen, 4);

			last = state[0] & 0x3F;
			padn = (last < 56) ? (56 - last) : (120 - last);

			md5_update(state, buffer, md5_padding, padn);
			md5_update(state, buffer, msglen, 8);

			PUT_ULONG_LE(state[2], output, 0);
			PUT_ULONG_LE(state[3], output, 4);
			PUT_ULONG_LE(state[4], output, 8);
			PUT_ULONG_LE(state[5], output, 12);
		}

#ifdef __cplusplus
	}
#endif
